[Federal Register Volume 60, Number 232 (Monday, December 4, 1995)]
[Proposed Rules]
[Pages 62061-62064]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-29453]



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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 95-93; Notice 01]
RIN 2127-AF76


Federal Motor Vehicle Safety Standards; Accelerator Control 
Systems

AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.

ACTION: Request for comments.

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SUMMARY: NHTSA is considering issuing a proposal to amend the Federal 
motor vehicle safety standard on accelerator control systems. The 
standard was last revised in 1973, when only mechanical systems were 
common on motor vehicles. In order to determine whether to propose 
amending the standard to include requirements specifically tailored for 
electronic accelerator control systems and to clarify possibly 
ambiguous language, NHTSA poses a series of questions in this document. 
NHTSA undertakes this action as part of its effort to implement the 
President's Regulatory Reinvention Initiative to make regulations 
easier to understand and to apply.

DATES: Comments must be received on or before February 2, 1996.

ADDRESSES: Comments must refer to the docket and notice numbers cited 
at the beginning of this notice and be submitted to: Docket Section, 
Room 5109, NHTSA, 400 Seventh Street SW., Washington, D.C. 20590. It is 
requested, but not required, that 10 copies of the comments be 
provided. The Docket Section is open on weekdays from 9:30 a.m. to 4 
p.m.

FOR FURTHER INFORMATION CONTACT: For non-legal issues: Mr. Patrick 
Boyd, Office of Vehicle Safety Standards, Office of Safety Performance 
Standards, NHTSA, 400 Seventh Street SW., Washington, D.C. 20590. Mr. 
Boyd's telephone number is (202) 366-6346, and his FAX number is (202) 
366-4329.
    For legal issues: Ms. Dorothy Nakama, Rulemaking Division, Office 
of Chief 

[[Page 62062]]
Counsel, NHTSA, 400 Seventh Street SW., Washington, D.C. 20590. Ms. 
Nakama's telephone number is (202) 366-2992, and her FAX number is 
(202) 366-3820. Please note that written comments should be sent to the 
Docket Section rather than faxed to the above contact persons.

SUPPLEMENTARY INFORMATION:

President's Regulatory Reinvention Initiative

    Pursuant to the March 4, 1995 directive ``Regulatory Reinvention 
Initiative'' from the President to the heads of departments and 
agencies, NHTSA undertook a review of its regulations and directives. 
During the course of this review, the agency identified rules that it 
could propose to eliminate as unnecessary or to amend to improve their 
comprehensibility, application or appropriateness. As described below, 
NHTSA has identified Federal Motor Vehicle Safety Standard (FMVSS) No. 
124, Accelerator control systems, as one rule that may benefit from 
amendments.

Background of Standard No. 124

    Standard No. 124's purpose is to reduce deaths and injuries 
resulting from loss of control of a moving vehicle's engine, due to 
malfunctions in the vehicle's accelerator control system. Since 1972, 
Standard No. 124 has specified requirements for ensuring the return of 
a vehicle's throttle to the idle position under each of the following 
two circumstances, (1) when the driver removes the actuating force 
(typically, the driver's foot or cruise control) from the accelerator 
control, and (2) when there is a severance or disconnection in the 
accelerator control system. Standard No. 124 applies to passenger cars, 
multipurpose passenger vehicles, trucks, and buses.
    Paragraph S5.1 of Standard No. 124 requires that, under any load 
condition, and within the time specified in S5.3, the throttle must 
return to the idle position from any accelerator position or any speed 
of which the engine is capable, whenever the driver removes the 
actuating force. The standard defines the throttle as ``the component 
of the fuel metering device that connects to the driver-operated 
accelerator control system and that by input from the driver-operated 
accelerator control system controls the engine speed.''
    Standard No. 124 has two further requirements to provide safety in 
the event of accelerator control failure. The first, specified at S5.1, 
requires ``at least two sources of energy,'' each capable of returning 
the throttle to idle position within the time limit for normal 
operation, from any accelerator position or speed whenever the driver 
removes the opposing actuating force. The second, specified at S5.2, 
requires that the throttle return to idle ``whenever any one component 
of the accelerator control system is disconnected or severed at a 
single point'' and the driver releases the pedal.
    Paragraph S5.3 requires that the throttle return to idle within 1 
second for vehicles of 10,000 pounds or less gross vehicle weight 
rating (GVWR) and within 2 seconds for vehicles with a GVWR greater 
than 10,000. The maximum allowable time is increased to 3 seconds for 
any vehicle that is exposed to ambient air at O degrees to -40 degrees 
F. during the test or for any portion of a 12 hour conditioning period.

Standard No. 124 Applies to Electronic Accelerator Control Systems

    When promulgated, the definitions and requirements of Standard No. 
124 were easy to understand and apply because their language was 
strongly influenced by the design of mechanical accelerator control 
systems and because all control systems were mechanical then. The 
``throttle'' of a gasoline engine was the carburetor shaft that opened 
and closed the air passages in the base plate. The ``throttle'' of a 
diesel engine was the control rod, or rack that controlled fuel flow to 
the high pressure injectors. The two energy sources were simply two 
return springs acting on the linkages and/or cables between the 
accelerator pedal and the throttle. If at least one of those springs 
was connected directly to the carburetor or to the diesel fuel 
injection rack, it would cause the throttle to return to idle in the 
event of a disconnection of the linkage. And, if the single 
contemplated failure occurred at one spring, the other would permit 
continued driver control.
    Subsequent to the promulgation of Standard No. 124, electronic 
accelerator controls with on-board computer systems were introduced on 
motor vehicles. Their use is steadily increasing, especially in heavy 
trucks.
    The introduction of electronic systems led to questions about their 
status and treatment under the Standard. Stating that some of the 
language in Standard No. 124 seemed more appropriate for mechanical 
accelerator control systems than for electronic ones, Isuzu Motors 
America, Inc., asked the agency a variety of questions concerning 
electronic systems. Its central question was whether the Standard 
applies to electronic systems. In an August 8, 1988 interpretation 
letter to Isuzu, NHTSA stated that the Standard does apply to 
electronic accelerator control systems. Among its other questions, 
Isuzu asked whether a severance in electric wires in its electronic 
accelerator control system is a severance within the meaning of S5.2 of 
Standard No. 124. Isuzu expressed its belief that because the electric 
wires were not a ``moving part,'' the answer should be ``no.'' NHTSA 
disagreed.
    It interpreted Standard No. 124's requirement that the throttle 
return to idle ``whenever any one component of the accelerator control 
system is disconnected or severed at a single point,'' to include all 
severances or disconnections of any component of the accelerator 
control system as within the standard, not just disconnections of 
moving parts.

Need To Amend Standard No. 124

    Most accelerator linkages on the largest classes of trucks (i.e., 
those over 33,001 lbs. GVWR) are now electronic. A mechanical 
accelerator linkage controlling a fuel rack (i.e., a device that 
controls fuel flow to the high pressure injectors) is now rare on the 
largest classes of trucks. Most of today's heavy diesel trucks have no 
mechanical connection between the accelerator pedal and the throttle.
    Although the agency has been issuing interpretations about the 
Standard's application to electronic accelerator control systems for 
the last seven years, the flow of interpretation requests remains 
unabated. Manufacturers continue to ask the basic question of whether 
the Standard applies to electronic accelerator control systems. One 
correspondent presumed that since those systems do not include springs 
and linkages, as described in Standard No. 124, electronic accelerator 
controls are not regulated. Another asked for a legal interpretation of 
``throttle,'' as applied to electronic accelerator control systems. 
Other correspondents have understood Standard No. 124 to mean simply 
that two return springs should be placed on the treadle assembly. In 
response, the agency has recited in its interpretation letters the 
requirement that the sources of energy must be capable of returning the 
throttle to idle in the event of a single severance or disconnection. 
The correspondents did not submit sufficient information to enable the 
agency to determine whether the proper mechanical operation of the 
treadle was sufficient to assure return to idle in the event of an 
electrical severance.
    NHTSA notes that although the use of two springs on the treadle 
assembly may 

[[Page 62063]]
represent good treadle design, it does not intrinsically overcome a 
disconnection anywhere within an electronic accelerator control system. 
Thus, good treadle design does not provide an electronic accelerator 
control system with the same degree of fail-safe operation provided a 
mechanical system by redundant return springs on a traditional fuel 
control rack. Those springs on a traditional rack could overcome an 
accelerator control disconnection and return the throttle to idle. 
Further, providing good treadle design does not solve the problem of 
single point disconnection in electronic systems which now would 
include connectors, wires, computer components and possibly even 
software elements. Even parties recognizing the analogy between wire 
severance and linkage severance have asked whether the standard applies 
to subsequent short circuits as well as open disconnections.
    NHTSA believes that the volume of requests for interpretation might 
be reduced if, instead of answering these questions by drawing 
analogies between traditional mechanical components and new electronic 
systems, it amended the Standard to include provisions and language 
specifically tailored to electronic systems. There are limitations to 
the agency's ability to make regulatory language, which reflects the 
design of mechanical systems, serve the purpose of regulating both 
mechanical and electronic systems. NHTSA also believes that amending 
the Standard not only to update it, but also possibly to redefine what 
constitutes fail safe operation might give manufacturers more 
flexibility in designing electronic systems and enable the agency to 
better ensure that electronic systems function safely. In order to do 
this, the agency must identify the most common predictable failures for 
electronic systems and ascertain the most appropriate response to those 
failures.
    NHTSA is also concerned that regulating electronic systems by 
drawing analogies to mechanical systems may have the effect of limiting 
the permissible responses to failures in electronic systems to the 
fail-safe modes of mechanical systems. At present, the failure modes 
(i.e., disconnection and severance) specified in Standard No. 124 are 
the predictable failure modes of a mechanical system. The agency 
believes that the regulation of electronic systems in a manner tailored 
to them can be beneficial to manufacturers, vehicle users, and the 
public. For example, with electronic systems, there may be failure 
modes in which it is wiser to either shut down the engine or to provide 
for a fail-safe mode in which the engine has just enough power to 
permit the vehicle to be driven to the side of the road, than to 
require that the engine be returned to idle. Since such choices were 
not feasible with mechanical controls, they were not included in 
Standard No. 124.
    Through this request for comments, NHTSA wishes to determine 
whether it can propose amendments which identify the predictable 
failure modes of electronic systems and specify an acceptable safe 
response for each mode.

Normal v. Failure Modes

    On many trucks, locking hand controls are necessary for the 
operation of engine-driven vocational equipment, i.e., work-performing 
equipment such as garbage compactors or cement mixers, when the vehicle 
is parked. Similar locking hand controls are also provided to 
facilitate engine warm-up. Obviously, locking hand controls can be 
thought of as preventing the return to normal idle speed when the 
accelerator pedal is released (defined in the Standard as a failure). 
Several requests for interpretation have resulted. However, locking 
hand controls do not affect highway safety because the locking controls 
are not meant to be used to drive vehicles. Explicit specification in 
the standard of what is or is not permissible with respect to the 
operation of locking hand controls could eliminate a source of 
ambiguity.
    Likewise, the lack of absolute repeatability in the normal 
operation of some electronic accelerator controls results in the return 
to a range of idle speeds instead of a single idle speed. While this 
range is narrow enough to permit safe operation of a vehicle, the 
return to a range of speeds instead of a single speed nevertheless 
introduces questions about whether a range is narrow enough to be 
regarded as complying with the requirements of the standard for return 
to idle speed. A revision of the standard offers an opportunity to 
adopt language that distinguishes between normal safe characteristics 
of accelerator controls and instances of failure.

Questions for Comment

    In order to determine whether the agency should propose to amend 
Standard No. 124 and to obtain a better idea of technology that is 
presently available, NHTSA asks the following questions to clarify 
engineering issues. Sections A and B apply to electronic systems only. 
Sections C, D, E and F are of general applicability.

A. Industry Consensus

    The Society of Automotive Engineers (SAE) has developed recommended 
practices for electronic signal interfaces for heavy diesel vehicle 
engine control processors and for some aspects of accelerator pedal 
position sensor performance. The SAE's recommended practice specifies 
that the accelerator position sensor (APS) assembly shall comply with 
all appropriate Federal motor vehicle safety standards.
    A1. Has the SAE or other industry consensus standards organizations 
considered fail-safe provisions for electronic accelerator controls? Is 
there industry agreement (informal or formal) concerning what fail-safe 
provisions should be adopted for electronic accelerator control 
systems?
    A2. What fail-safe strategies are now being employed by vehicle and 
component manufacturers?

B. Technical Considerations of a Fail-Safe Electronic Accelerator 
Control System

    NHTSA believes that the potential points of failure of an 
electronic accelerator control system are:

--the mechanical linkage and return springs between the pedal and the 
accelerator position sensor (APS);
--the electrical connections between the APS and the engine control 
processor;
--the electrical connections between the engine control processor and 
other critical sensors;
--the electrical connections between the engine control processor and 
fuel or air metering devices which determine engine speed;
--power to the engine control processor, the APS and critical sensors; 
and
--the integrity of the engine control processor, APS, and other 
critical sensors.

    A single point disconnection would mean the severance of a single 
wire or the disconnection of all the terminals housed in a single 
connector. The consequences both of an open circuit or a short circuit 
would ordinarily be relevant, but NHTSA does not exclude the 
possibility that some designs could prevent either a short circuit or 
an open circuit in the event of a disconnection. Critical sensors are 
those whose malfunction or disconnection could cause a significant 
uncontrolled engine overspeed. The agency is not aware that sensors 
other than the APS are critical in a safety sense.
    With this background, NHTSA asks the following questions:
    B1. Are there other predictable points of failure of an electronic 
control system? 

[[Page 62064]]

    B2. Are sensors other than the APS critical to safety on either 
gasoline or diesel engines?
    B3. Are engine development trends pushing other sensors toward 
safety critical operation (i.e., to become a sensor whose malfunction 
or disconnection could cause a significant uncontrolled engine 
overspeed)?
    B4. Is it practical (from an engineering standpoint) to expect a 
fail-safe design of a unitary electronic accelerator control system, 
even in the limited sense of ensuring fail-safe performance in the case 
of single point failures at predictable locations? Would it be more 
practical (and still meet the need for safety) to use a redundant, 
simplified APS and engine controller, active only at the idle position 
of the pedal? Is the use of redundant systems more practical than a 
single system to achieve fail-safe performance?
    B5. Do any currently produced vehicles with electronic accelerator 
control systems use redundancy to achieve fail-safe operation?

C. Vehicle Drive Functions v. Vocational Functions

    NHTSA legal interpretations regarding hand throttle controls view 
their operation as setting a new idle speed to which the throttle 
should return in the prescribed time limits ``upon release of the 
driver-operated accelerator control system.'' This view is accurate for 
traditional ``fast idle'' setting devices for cold engine operation. 
But, it may also have resulted in interpretations that do not 
distinguish between accelerator control systems that drive the vehicle, 
and auxiliary accelerator controls meant to allow the operation of 
vocational equipment (such as the compactor on a garbage truck) on a 
parked vehicle.
    C1. How is the cold engine fast idle function accomplished with 
electronic accelerator controls?
    C2. How is the engine of a parked vehicle held at the appropriate 
speed to operate vocational equipment when the vehicle is equipped with 
an electronic accelerator control system?
    C3. Is there a general way to distinguish between accelerator 
controls affecting the driving of the vehicle and those affecting only 
the vehicle's operation as a power source for vocational equipment, 
presumably without effect on highway safety?

D. Initial Idle Speed

    Manufacturers have been concerned with the question of how 
consistently a vehicle's engine must return to exactly the same idle 
speed to meet Standard No. 124. Apparently, the resolution and 
hysteresis of the various sensors and the discrete nature of digital 
systems create idle speed variations that do not in any way indicate 
failure.
    D1. Would it be practical to designate a range about a vehicle's 
initial idle speed to clarify the difference between normal and 
abnormal performance of an accelerator control system? Please describe 
the desirable extent of such a range and provide a rationale for that 
range.

E. Public Technical Meeting

    NHTSA believes that the development of any proposal to amend 
Standard No. 124 may benefit from a direct, oral exchange of ideas 
among NHTSA, vehicle manufacturers, and other affected parties. 
Reliance solely on written public comments may not be the most 
effective means of assessing the appropriate steps for ensuring the 
safe operation of electronic accelerator control systems.
    E1. Once the agency has analyzed the written comments submitted in 
response to this document, should it hold a public technical meeting to 
discuss possible proposals for amending the Standard No. 124? If so, on 
which issues should such a public technical meeting focus?

F. Other Issues

    F1. Should the agency propose to amend Standard No. 124 in any 
other respect that has not been discussed above? If so, please describe 
how the agency should propose to amend the Standard, and provide a 
rationale for the recommended change.

Rulemaking Analyses and Notices

1. Executive Order 12866 and DOT Regulatory Policies and Procedures

    This request for comment was not reviewed under Executive Order 
12866 (Regulatory Planning and Review). NHTSA has analyzed the impact 
of this request for comment and determined that it is not 
``significant'' within the meaning of the Department of 
Transportation's regulatory policies and procedures. The agency 
anticipates if a proposal and ultimately a final rule should result 
from this request for comment, new requirements would not be imposed on 
manufacturers with respect to the currently regulated systems. The 
request for comment seeks to find cost effective means to make Standard 
No. 124 more understandable when applied to electronic accelerator 
control systems. If NHTSA decides to initiate rulemaking, it is NHTSA's 
intent that the rulemaking not impose any additional costs.

Procedures for Filing Comments

    Interested persons are invited to submit comments on this request 
for comment. It is requested but not required that 10 copies be 
submitted.
    All comments must not exceed 15 pages in length. (49 CFR 553.21). 
Necessary attachments may be appended to these submissions without 
regard to the 15-page limit. This limitation is intended to encourage 
commenters to detail their primary arguments in a concise fashion.
    If a commenter wishes to submit certain information under a claim 
of confidentiality, three copies of the complete submission, including 
purportedly confidential business information, should be submitted to 
the Chief Counsel, NHTSA, at the street address given above, and seven 
copies from which the purportedly confidential information has been 
deleted should be submitted to the Docket Section. A request for 
confidentiality should be accompanied by a cover letter setting forth 
the information specified in the agency's confidential business 
information regulation. 49 CFR part 512.
    All comments received before the close of business on the comment 
closing date indicated above for the proposal will be considered, and 
will be available for examination in the docket at the above address 
both before and after that date. To the extent possible, comments filed 
after the closing date will also be considered. Comments received after 
the comment due date will be considered as suggestions for any future 
rulemaking action. Comments on the request for comment will be 
available for inspection in the docket. The NHTSA will continue to file 
relevant information as it becomes available in the docket after the 
closing date, and it is recommended that interested persons continue to 
examine the docket for new material.
    Those persons desiring to be notified upon receipt of their 
comments in the rules docket should enclose a self-addressed, stamped 
postcard in the envelope with their comments. Upon receiving the 
comments, the docket supervisor will return the postcard by mail.

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50.

    Issued on: November 28, 1995.
Barry Felrice,
Associate Administrator for Safety Performance Standards.
[FR Doc. 95-29453 Filed 12-1-95; 8:45 am]
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